Search Publications
A Hubble Space Telescope Census of Nuclear Star Clusters in Late-Type Spiral Galaxies. II. Cluster Sizes and Structural Parameter Correlations
Böker, Torsten; Ho, Luis C.; Shields, Joseph C. +4 more
We investigate the structural properties of nuclear star clusters in late-type spiral galaxies. More specifically, we fit analytical models to Hubble Space Telescope images of 39 nuclear clusters in order to determine their effective radii after correction for the instrumental point-spread function. We use the results of this analysis to compare t…
Magnetic Reconnection and Mass Acceleration in Flare-Coronal Mass Ejection Events
Qiu, Jiong; Wang, Haimin; Gary, Dale E. +1 more
An observational relationship has been well established among magnetic reconnection, high-energy flare emissions and the rising motion of erupting flux ropes. In this paper, we verify that the rate of magnetic reconnection in the low corona is temporally correlated with the evolution of flare nonthermal emissions in hard X-rays and microwaves, all…
A Probable z~7 Galaxy Strongly Lensed by the Rich Cluster A2218: Exploring the Dark Ages
Richard, Johan; Ellis, Richard S.; Kneib, Jean-Paul +1 more
We discuss the observational properties of a remarkably faint triply imaged galaxy revealed in a deep z'-band Advanced Camera for Surveys observation of the lensing cluster A2218 (z=0.175). A well-constrained mass model for the cluster, which incorporates the outcome of recent Keck spectroscopic campaigns, suggests that the triple syste…
A Composite Extreme-Ultraviolet QSO Spectrum from FUSE
Green, Richard F.; Shull, J. Michael; Scott, Jennifer E. +4 more
The Far Ultraviolet Spectroscopic Explorer (FUSE) has surveyed a large sample (>100) of active galactic nuclei (AGNs) in the low-redshift universe (z<1). Its response at short wavelengths makes it possible to measure directly the far-ultraviolet spectral properties of quasi-stellar objects (QSOs) and Seyfert 1 galaxies at z<0.3. Using arc…
Hubble Space Telescope Absolute Spectrophotometry of Vega from the Far-Ultraviolet to the Infrared
Bohlin, R. C.; Gilliland, R. L.
The Space Telescope Imaging Spectrograph (STIS) has measured the absolute flux for Vega from 0.17-1.01 µm on the Hubble Space Telescope white dwarf (WD) flux scale. These data are saturated by up to a factor of 80 overexposure but retain linearity to a precision of 0.2% because the charge bleeds along the columns and is recovered during read…
The structure and environment of young stellar clusters in spiral galaxies
Larsen, S. S.
A search for stellar clusters has been carried out in 18 nearby spiral galaxies, using archive images from the Wide Field Planetary Camera 2 on board the Hubble Space Telescope. All of the galaxies have previously been imaged from the ground in UBVI. A catalogue of structural parameters, photometry and comments based on visual inspection of the cl…
Synopsis of the interstellar He parameters from combined neutral gas, pickup ion and UV scattering observations and related consequences
Möbius, E.; Noda, H.; Bzowski, M. +17 more
A coordinated effort to combine all three methods that are used to determine the physical parameters of interstellar gas in the heliosphere has been undertaken. In order to arrive at a consistent parameter set that agrees with the observations of neutral gas, pickup ions and UV backscattering we have combined data sets from coordinated observation…
Double-barred galaxies. I. A catalog of barred galaxies with stellar secondary bars and inner disks
Erwin, Peter
I present a catalog of 67 barred galaxies which contain distinct, elliptical stellar structures inside their bars. Fifty of these are double-barred galaxies: a small-scale, inner or secondary bar is embedded within a large-scale, outer or primary bar. I provide homogenized measurements of the sizes, ellipticities, and orientations of both inner an…
ILCT: Recovering Photospheric Velocities from Magnetograms by Combining the Induction Equation with Local Correlation Tracking
Welsch, B. T.; Fisher, G. H.; Abbett, W. P. +1 more
We present three methods for deriving the velocity field in magnetized regions of the Sun's photosphere. As a preliminary step, we introduce a Fourier-based local correlation tracking (LCT) routine that we term ``FLCT.'' By explicitly employing the observation made by Démoulin & Berger, that results determined by LCT applied to magnetograms in…
Changes in the X-Ray Emission from the Magnetar Candidate 1E 2259+586 during Its 2002 Outburst
Heyl, J.; Marshall, H. L.; Chakrabarty, D. +6 more
An outburst of more than 80 individual bursts, similar to those seen from Soft Gamma Repeaters (SGRs), was detected from the anomalous X-ray pulsar (AXP) 1E 2259+586 in 2002 June. Coincident with this burst activity were gross changes in the pulsed flux, persistent flux, energy spectrum, pulse profile, and spin-down of the underlying X-ray source.…